It is estimated that 17-34 million have a varying stage of diabetic retinopathy (DR)1. In the US, it is the leading cause of blindness in working age adults and remains a public health problem throughout the world. The earliest manifestations of DR are believed to originate in capillary occlusion 2 resulting in both hypo- and hyperperfusion of regional capillaries. Additionally, vascular associated cells called pericytes which ensheathe the capillary endothelium, are characteristically lost with DR progression3,4. And while these manifestations have been identified as hallmarks of the disease, the pathogenic chronology of these events remain unclear. A major obstacle in identifying the primary and associated cause of capillary infarction, regression and proliferation has been lack of sufficient resolution to identify these microscopic events in the living eye. Traditional fundoscopy approaches lack necessary resolution to resolve sub-cellular structure because the eye's optics blur the retinal image. Therefore, we will use an adaptive optics scanning laser ophthalmoscope (AOSLO) which corrects for the eyes aberrations to achieve sub-cellular resolution needed for this research. Because AOSLO is non-invasive, a benefit of this approach is that the same subjects can be imaged over longitudinal progression of the disease; not requiring post-mortem analysis to acquire sufficient resolution. We will image both pericytes and capillary blood flow in a transgenic mouse model expressing fluorescent pericytes. In this model, we will induce a condition similar to human type-1 diabetes mellitus by injecting streptozotocin, an agent that selectively destroys insulin producing -cells in the pancreas. By tracking the progressive changes in capillary flow and pericyte density in the same animals over the course of weeks, we seek to better understand the chronology of the earliest events related to the human form of DR!